N = int(input())
c = list(input())

ans = 0
left = 0
right = N-1
while left < right:
    if c[left] != c[right]:
        if c[left] == 'W' and c[right] == 'R':
            ans += 1
        left += 1
        right -=1
        
    if c[left] == 'R' and c[right] == 'R':
        left += 1
    if c[left] == 'W' and c[right] == 'W':
        right -=1
        
print(ans) N = int(input()) N int(input()) int input() input c = list(input()) c list(input()) list input() input ans = 0 ans 0 left = 0 left 0 right = N-1 right N-1 N 1 while left < right:
    if c[left] != c[right]:
        if c[left] == 'W' and c[right] == 'R':
            ans += 1
        left += 1
        right -=1
        
    if c[left] == 'R' and c[right] == 'R':
        left += 1
    if c[left] == 'W' and c[right] == 'W':
        right -=1
         left < right left right if c[left] != c[right]:
        if c[left] == 'W' and c[right] == 'R':
            ans += 1
        left += 1
        right -=1
        
     c[left] != c[right] c[left] c left c[right] c right if c[left] == 'W' and c[right] == 'R':
            ans += 1
         c[left] == 'W' and c[right] == 'R' c[left] == 'W' c[left] c left 'W' c[right] == 'R' c[right] c right 'R' ans += 1 ans 1 left += 1 left 1 right -=1 right 1 if c[left] == 'R' and c[right] == 'R':
        left += 1
     c[left] == 'R' and c[right] == 'R' c[left] == 'R' c[left] c left 'R' c[right] == 'R' c[right] c right 'R' left += 1 left 1 if c[left] == 'W' and c[right] == 'W':
        right -=1
         c[left] == 'W' and c[right] == 'W' c[left] == 'W' c[left] c left 'W' c[right] == 'W' c[right] c right 'W' right -=1 right 1 print(ans) print ans right = N-1 N-1 right ans = 0 0 ans left += 1 1 left ans += 1 1 ans left = 0 0 left right -=1 1 right c = list(input()) list(input()) c N = int(input()) int(input()) N left += 1 1 left right -=1 1 right
N = int(input())
c = list(input())

ans = 0
left = 0
right = N-1
while left < right:
    if c[left] != c[right]:
        if c[left] == 'W' and c[right] == 'R':
            ans += 1
        left += 1
        right -=1
        
    if c[left] == 'R' and c[right] == 'R':
        left += 1
    if c[left] == 'W' and c[right] == 'W':
        right -=1
        
print(ans)